DTS being downmixed to 2 channel AC3, why?

[gertgerman]

Hi All,

using a win 8.1 PC with nightly 6910. In the process of moving all my physical media to a media server and have always tried to have an AAC 2.0 track and an AC3 5.1 track for optimum compatibility with all my devices. In the past this has worked fine using the preset normal, audio 1 set to codec AAC (avcodec) and audio 2 to codec AC3 Passthru. Of late I've noticed when the source track is a DTS 5.1 track I am no longer getting an AC3 5.1 track output but rather an AC3 2.0 track. the log file:

[21:30:53] * audio track 1
[21:30:53] + decoder: English (DTS) (5.1 ch) (track 2, id 0x2)
[21:30:53] + bitrate: 1536 kbps, samplerate: 48000 Hz
[21:30:53] + mixdown: Dolby Pro Logic II
[21:30:53] + encoder: AAC (libavcodec)
[21:30:53] + bitrate: 160 kbps, samplerate: 48000 Hz
[21:30:53] * audio track 2
[21:30:53] + decoder: English (DTS) (5.1 ch) (track 2, id 0x2)
[21:30:53] + bitrate: 1536 kbps, samplerate: 48000 Hz
[21:30:53] + mixdown: Dolby Pro Logic II
[21:30:53] + encoder: AC3 (libavcodec)
[21:30:53] + bitrate: 224 kbps, samplerate: 48000 Hz
[21:30:53] * audio track 3
[21:30:53] + decoder: Deutsch (DTS) (5.1 ch) (track 1, id 0x1)
[21:30:53] + bitrate: 1536 kbps, samplerate: 48000 Hz
[21:30:53] + mixdown: Dolby Pro Logic II
[21:30:53] + encoder: AAC (libavcodec)
[21:30:53] + bitrate: 160 kbps, samplerate: 48000 Hz
[21:30:53] * audio track 4
[21:30:53] + decoder: Deutsch (DTS) (5.1 ch) (track 1, id 0x1)
[21:30:53] + bitrate: 1536 kbps, samplerate: 48000 Hz
[21:30:53] + mixdown: Dolby Pro Logic II
[21:30:53] + encoder: AC3 (libavcodec)
[21:30:53] + bitrate: 224 kbps, samplerate: 48000 Hz

any ideas as to why this now downmixes to AC3 2.0 rather than keeping the 5.1 and what I need to change the setting to to get AC3 5.1 from a DTS 5.1 source?

thanks in advance.

[Woodstock]

Have the complete log, which includes the parameters used to start the encode, would be very helpful.

[gertgerman]

I installed the latest final version of handbrake and the problem was resolved but again after changing to a nightly build DTS 5.1 is being converted to an AC3 2.0 rather than an AC3 5.1 track. My full log is attached.

http://pastebin.com/Sed8CvVt

thanks

[moneymatt4life]

... that's because dolby pro logic II downmixes 5.1ch to stereo

[JohnAStebbins]

The log indicates that this is what the GUI selected (Dolby DPLII, which is stereo). I'm not sure how the windows GUI works in this scenario. But the linux GUI lets you set the mixdown, even when a passthru option is selected, for the case that it has to fall back to encoding.

So in the linux GUI, you would add the second audio track on the audio defaults pane, set AC-3 passthru as the codec, then set the additional parameters to whatever you want to happen when it has to fall back to AC-3 encoding. Then save this as a new preset so you never have to do this step again

Hopefully someone that uses the windows GUI will chime in with details of how this works there.

[gertgerman]

... that's because dolby pro logic II downmixes 5.1ch to stereo

so what do I need to change as I set it to AC3 passthru and on the final version of handbrake it outputs AC3 5.1. I cant see anywhere I can set it to default to AC3 5.1 as opposed to dolby pro logic II

[gertgerman]

The log indicates that this is what the GUI selected (Dolby DPLII, which is stereo). I'm not sure how the windows GUI works in this scenario. But the linux GUI lets you set the mixdown, even when a passthru option is selected, for the case that it has to fall back to encoding.

So in the linux GUI, you would add the second audio track on the audio defaults pane, set AC-3 passthru as the codec, then set the additional parameters to whatever you want to happen when it has to fall back to AC-3 encoding. Then save this as a new preset so you never have to do this step again

Hopefully someone that uses the windows GUI will chime in with details of how this works there.

Could I set it the codec to AC3 rather than AC3 passthru and then the mixdown to 5.1 channels and save as a new preset? Would that essentially do the same?

[JohnAStebbins]

The log indicates that this is what the GUI selected (Dolby DPLII, which is stereo). I'm not sure how the windows GUI works in this scenario. But the linux GUI lets you set the mixdown, even when a passthru option is selected, for the case that it has to fall back to encoding.

So in the linux GUI, you would add the second audio track on the audio defaults pane, set AC-3 passthru as the codec, then set the additional parameters to whatever you want to happen when it has to fall back to AC-3 encoding. Then save this as a new preset so you never have to do this step again

Hopefully someone that uses the windows GUI will chime in with details of how this works there.

Could I set it the codec to AC3 rather than AC3 passthru and then the mixdown to 5.1 channels and save as a new preset? Would that essentially do the same?

It will do what you want with DTS audio. But it will re-encode AC3 audio which would result in some amount of quality loss.

[gertgerman]

The log indicates that this is what the GUI selected (Dolby DPLII, which is stereo). I'm not sure how the windows GUI works in this scenario. But the linux GUI lets you set the mixdown, even when a passthru option is selected, for the case that it has to fall back to encoding.

So in the linux GUI, you would add the second audio track on the audio defaults pane, set AC-3 passthru as the codec, then set the additional parameters to whatever you want to happen when it has to fall back to AC-3 encoding. Then save this as a new preset so you never have to do this step again

Hopefully someone that uses the windows GUI will chime in with details of how this works there.

Could I set it the codec to AC3 rather than AC3 passthru and then the mixdown to 5.1 channels and save as a new preset? Would that essentially do the same?

It will do what you want with DTS audio. But it will re-encode AC3 audio which would result in some amount of quality loss.

That's fine AC3 passthru on AC3 5.1 sources works fine so I can use that preset, only when I use it for DTS sources does it change to DPLII so all good. Thanks for the help

[moneymatt4life]

WinGUI doesn't allow setting the fallback bitrate/mixdown currently, so nothing you can do as of yet in that regard... so when loading sources with DTS audio you have to manually specify AC3 instead of AC3 Passthru... which, if you don't have that many sources with DTS audio, shouldn't be that bothersome in the longrun...

[Deleted User 11865]

Something is wrong though: the default mixdown for the AC-3 encoder is 5.1; the Windows GUI must be setting it to DPL2 somehow.

[s55]

Yup. It's just defaulting it to AC3.

In this case, auto-passthru with AC3 and DTS selected as the options would work fine.